Since the clamping and setting up of a workpiece in a machine tool often makes up a considerable part of the machining time, it is advantageous if the exact positions of the workpiece and its clamping devices can be detected as fast as possible. Various devices and methods have already been proposed for this purpose which use cameras for detecting the clamping condition.
German Patent Document DE 11 2007 001 977 T5, for example, describes a method which extracts a model of a workpiece from a camera image of the workpiece. The techniques used for this purpose, such as detection of edges, are described in detail. The model is then compared to known objects to identify the particular object present. The position and orientation of the object are later determined from the camera image and used, for example, for collision control.
German Patent Document DE 10 2005 022 344 A1 also describes a method which allows the position of a workpiece to be determined, at least roughly, from geometrical parameters which are obtained from a camera image and reconciled with a model of the workpiece. The information so obtained is either used as a starting position for an even more accurate measurement using a tactile sensor, or used directly to determine a matrix which describes a displacement and/or a rotation of the workpiece relative to a reference point of the machine tool. This allows accurate machining of the workpiece even when the actual clamping condition does not exactly match the clamping condition expected by the NC program.